Maybe someone here can help out with digital filter design.

I have a filter with the transfer function:

y(z)= [ b0*x(z) + b1*x(z)*z^-1 ] / [1 - a1*z^-1 ]

I cannot recall how to determine the frequencies of the poles and zeros of
the filter.  Been too long since studying the z-transform.  Any help?

Regards,

Vincent Deno